U.S. patent number 7,408,341 [Application Number 11/599,297] was granted by the patent office on 2008-08-05 for rotation angle detection device.
This patent grant is currently assigned to Aisin Seiki Kabushiki Kaisha. Invention is credited to Hisayoshi Okuya, Kota Saito.
United States Patent |
7,408,341 |
Okuya , et al. |
August 5, 2008 |
Rotation angle detection device
Abstract
A rotation angle detection device includes a housing including a
magnetic sensor, a rotation member rotatable relative to the
housing and including a magnet facing the magnetic sensor, and a
shaft member operated so as to rotate with an operated member. A
rotation angle of the operated member is detected on the basis of a
change of an output signal from the magnetic sensor rotatable
relative to the magnet. The rotation member and the shaft member
are connected to each other in such a manner that axes thereof are
tiltable towards each other. Further, the rotation angle detection
device includes a centering mechanism for retaining the rotation
member and the housing member in a coaxial manner regardless of a
tilting of the shaft member.
Inventors: |
Okuya; Hisayoshi (Nishio,
JP), Saito; Kota (Nagoya, JP) |
Assignee: |
Aisin Seiki Kabushiki Kaisha
(Aichi-ken, JP)
|
Family
ID: |
38040098 |
Appl.
No.: |
11/599,297 |
Filed: |
November 15, 2006 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20070108967 A1 |
May 17, 2007 |
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Foreign Application Priority Data
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Nov 15, 2005 [JP] |
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2005-330391 |
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Current U.S.
Class: |
324/207.25;
324/207.2 |
Current CPC
Class: |
G01D
5/145 (20130101); G01D 2205/80 (20210501) |
Current International
Class: |
G01B
7/30 (20060101) |
Field of
Search: |
;73/1.79,121,130,132
;324/207.2,207.12,207.21,207.25,207.22 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Assouad; Patrick
Assistant Examiner: Schindler; David M.
Attorney, Agent or Firm: Reed Smith LLP Fisher, Esq.;
Stanley P. Marquez, Esq.; Juan Carlos A.
Claims
The invention claimed is:
1. A rotation angle detection device, comprising: a housing
including a magnetic sensor; a rotation member rotatable relative
to the housing and including a magnet facing the magnetic sensor; a
shaft member operated so as to rotate with an operated member, a
rotation angle of the operated member being detected on the basis
of a change of an output signal from the magnetic sensor rotatable
relative to the magnet; the rotation member and the shaft member
being connected to each other in such a manner that axes thereof
are tiltable towards each other; and a centering mechanism for
retaining the rotation member and the housing in a coaxial manner
regardless of a tilting of the shaft member.
2. A rotation angle detection device according to claim 1, wherein
the axis of the rotation member and a fixed axis of the housing are
coaxially maintained.
3. A rotation angle detection device according to claim 2, wherein
the centering mechanism includes an inclined face formed in the
housing and extending in a circumferential direction centered at
the fixed axis, and the centering mechanism includes a biasing
means for biasing an edge portion formed at axially one end of the
rotation member to be pressed against the inclined face of the
housing.
4. A rotation angle detection device according to claim 3, wherein
the rotation member includes a rotation restricting portion while
the shaft member includes a restricted portion that comes in
contact with the rotation restricting portion based on a rotation
of the rotation member in a predetermined direction relative to the
shaft member, and the biasing means is a coil spring that biases
the rotation member to be pressed against the inclined face of the
housing and at the same time that biases the rotation member to
rotate in the predetermined direction relative to the shaft
member.
5. A rotation angle detection device according to claim 2, wherein
the housing is of a cylindrical shape and includes a
cylindrical-shaped boss portion projecting from a center of the
housing.
6. A rotation angle detection device according to claim 5, wherein
the boss portion accommodates therein a Hall element by insert
molding.
7. A rotation angle detection device according to claim 2, wherein
the rotation member includes a cup-shaped yoke main body and a
magnet holder made of a nonmagnetic material and provided on an
inner peripheral face of the yoke main body, the magnet holder
accommodating the magnet therein.
8. A rotation angle detection device according to claim 5, wherein
the centering mechanism includes an inclined face in the housing
and having an inclination of approximately 45 degrees relative to
the fixed axis of the boss portion of the housing.
9. A rotation angle detection device according to claim 7, wherein
the magnet holder includes an annular edge portion.
10. A rotation angle detection device according to claim 9, wherein
the edge portion of the magnet holder forms an external angle of
approximately 100 degrees relative to the fixed axis of the housing
in a cross-section passing through the fixed axis of the
housing.
11. A rotation angle detection device according to claim 10,
wherein a diameter of an inner peripheral face of the edge portion
of the magnet holder is specified to be larger than an outer
diameter of the boss portion.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
This application is based on and claims priority under 35 U.S.C.
.sctn. 119 to Japanese Patent Application No. 2005-330391, filed on
Nov. 15, 2005, the entire content of which is incorporated herein
by reference.
FIELD OF THE INVENTION
This invention generally relates to a rotation angle detection
device.
BACKGROUND
A known rotation angle detection device is disclosed in
JP2001-317909A. The rotation angle detection device disclosed
includes a housing equipped with a Hall IC (magnetic sensor), a
rotation shaft (shaft member) operated so as to rotate as a unit
with an operated member, and a rotor core (rotation member) having
a magnet. When the rotor core rotates along with a rotation of the
operated member such as a throttle valve, in response to a rotation
angle of the rotor core, a magnetic flux density passing through
the Hall IC varies. Then, in response to this magnetic flux
density, an output of the Hall IC varies. A control circuit reads
this output of the Hall IC and then detects a rotation angle of the
rotor core and the operated member.
However, according to the aforementioned rotation angle detection
device, the rotor core and the rotation shaft are integrally fixed
to each other by means of riveting, and the like. That is, the
rotor core and the rotation shaft are not rotatable relative to
each other and are connected in such a manner that axes of the
rotor core and the rotation shaft are not tiltable to each other.
When a stress involving a tilting component, i.e. a stress that
causes the axis of the rotation shaft to tilt relative to a fixed
axis of the housing, is added to the rotation shaft via the
operated member, a position of the magnet provided at the rotor
core relative to the Hall IC provided at the housing is changed,
thereby decreasing rotation angle detecting accuracy.
Thus, a need exists for a rotation angle detection device of which
rotation angle detecting accuracy is prevented from decreasing even
if a stress involving a tilt component is applied to a shaft member
via an operated member.
SUMMARY OF THE INVENTION
According to an aspect of the present invention, a rotation angle
detection device includes a housing including a magnetic sensor, a
rotation member rotatable relative to the housing and including a
magnet facing the magnetic sensor, and a shaft member operated so
as to rotate with an operated member. A rotation angle of the
operated member is detected on the basis of a change of an output
signal from the magnetic sensor rotatable relative to the magnet.
The rotation member and the shaft member are connected to each
other in such a manner that axes thereof are tiltable towards each
other. Further, the rotation angle detection device includes a
centering mechanism for retaining the rotation member and the
housing member in a coaxial manner regardless of a tilting of the
shaft member.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing and additional features and characteristics of the
present invention will become more apparent from the following
detailed description considered with reference to the accompanying
drawings, wherein:
FIG. 1A is a schematic side view of a control pedal unit equipped
with a rotation angle detection device according to an embodiment
of the present invention;
FIG. 1B is a schematic front view of the control pedal unit
equipped with the rotation angle detection device according to the
embodiment of the present invention;
FIG. 2 is a cross-sectional front view of the rotation angle
detection device according to the embodiment of the present
invention;
FIG. 3 is a cross-sectional front view of the rotation angle
detection device before assembly;
FIG. 4 is a cross-sectional side view of a main portion of the
rotation angle detection device;
FIG. 5 is a cross-sectional side view of a main portion of the
rotation angle detection device;
FIG. 6 is an exploded perspective view of the rotation angle
detection device; and
FIGS. 7A, 7B, 7C, 7D, 7E, and 7F are schematic views of various
centering mechanisms.
DETAILED DESCRIPTION
An embodiment of the present invention will be explained with
reference to the attached drawings. FIGS. 1A and 1B are schematic
views of a control pedal unit 2 such as a brake pedal provided in a
vehicle. Precisely, FIG. 1A is a side view of a rotation angle
detection device 4 incorporated in the control pedal unit 2. FIG.
1B is a front view of the control pedal unit 2. As shown in FIG.
1B, the control pedal unit 2 includes a pedal arm 3 supported,
being rotatable relative to a bracket 1 about an axis X1 thereof,
the bracket 1 being mounted on a vehicle body so as to project
therefrom, and the rotation angle detection device 4 that detects a
rotation angle of the pedal arm 3 operated by a driver.
As shown in FIG. 2, the rotation angle detection device 4 includes
a housing 5 made of plastic and including a magnetic unit 7a, a
rotation member 10 accommodated within the housing 5, and a shaft
member 15 pivotally supported by a portion of the housing 5. The
shaft member 15 is fixed by means of riveting, and the like, to a
base portion of a sensor lever 16 (example of an operated member)
so that the shaft member 15 is prevented from rotating and
inclining relative to the sensor lever 16. In addition, a bended
end portion 16a of the sensor lever 16 is constantly pressed
against a pedal lever 3a integrally extending from the pedal arm 3.
The rotation member 10 includes two pairs of permanent magnets 13
while the magnetic unit 7a of the housing 5 includes one pair of
Hall ICs 7 (example of a magnetic sensor) arranged so as to face
the permanent magnets 13, and a capacitor for noise removal (not
shown). In addition, the housing 5 includes a connector portion 8
for acquiring an output signal from the Hall ICs 7.
The sensor lever 16 is fixed to the shaft member 15 in a
cantilevered manner. Further, the pedal lever 3a operates to rotate
the sensor lever 16 in a position displaced from the shaft member
15 along a direction of the axis X1. Thus, a stress added from the
pedal lever 3a to the sensor lever 16 is likely to cause the shaft
member 15 to incline or tilt relative to the housing 5. When the
pedal arm 3 is operated to rotate by means of a depression of a
pedal by a driver, the pedal lever 3a and the shaft member 15
rotate as a unit in response to the rotation amount of the pedal
arm 3 within a range shown by a curved arrow in FIG. 1A, thereby
rotating the rotation member 10. The Hall ICs 7 of the housing 5
are arranged in a position where a magnetic flux is applied from
the permanent magnets 13 provided at the rotation member 10.
Therefore, a rotation angle of the sensor lever 16 can be acquired
from the connector portion 8 as a change in an output signal from
the Hall ICs 7 that relatively rotate to the permanent magnets
13.
More precisely, as shown in FIGS. 2 and 3, the housing 5 includes a
housing main body 5a having the magnetic unit 7a, the connector
portion 8, and a substantially cylindrical receiving portion 5t,
and a cover member 5b for tightly closing or covering the receiving
portion 5t. The housing main body 5a and the cover member 5b are
made of plastic and fixed to each other by laser welding, and the
like. A substantially column-shaped boss portion 6 is formed in the
vicinity of a center of the housing main body 5a so as to project
towards the shaft member 15. The pair of Hall ICs 7 are
accommodated within the boss portion 6 by insert-molding. The shaft
member 15 is pivotally supported by a cylindrical-shaped bearing 5c
formed in the vicinity of a center of the cover member 5b. The
housing 5 is fixed by screwing to a vehicle body through a pair of
fitting brackets 50 formed, integrally extending from the housing
main body 5a in a direction where the pair of fitting brackets 50
oppose to or separate from each other, as shown in FIG. 1A. The
rotation member 10 includes a cup-shaped yoke main body 11 and a
magnet holder 12 fixed to an inner peripheral face of the yoke main
body 11. The yoke main body 11 is made of a magnetic material such
as iron and nickel alloy while the magnet holder 12 is made of a
non-magnetic material such as plastic. The permanent magnets 13 are
supported and received within the magnet holder 12. The yoke main
body 11 equipped with the permanent magnets 13 constitutes a kind
of a magnetic circuit.
According to one of the features of the rotation angle detection
device 4 of the present embodiment, the rotation member 10 and the
shaft member 15 are connected to each other in such a manner that
axes thereof are tiltable to each other. That is, as shown in FIGS.
4 and 5, the shaft member 15 includes a cross-section of which a
circumference is not in a rotational symmetrical shape, which is
effective for transmission of a rotational driving force.
Meanwhile, the yoke main body 11 includes a through-hole 11H in the
vicinity of a bottom face, corresponding to the cross-section of
the shaft member 15. A size of the through-hole 11H is formed to be
slightly larger than that of the section of the shaft member 15.
Thus, the rotation member 10 can be tilted in any direction
relative to the shaft member 15. Even if the shaft member 15 is
tilted relative to the housing 5 in the cases where the sensor
lever 16 is operated to rotate by means of the pedal lever 3a, the
rotation member 10 provided within the housing 5 is not forced to
tilt. At this time, the rotation member 10 into which the shaft
member 15 is disposed is prevented from disengaging from the shaft
member 15 by means of a bolt 15B having a head portion projecting
further in a radial direction than the section of the shaft member
15.
A rotation transmitting mechanism is provided between the rotation
member 10 and the shaft member 15 so as to transmit a rotation of
the shaft member 15 to the rotation member 10. Precisely, as shown
in FIGS. 4 and 5, the through-hole 11H of the rotation member 10
includes a pair of rotation restricting faces 20a (example of a
rotation restricting portion) that face each other relative to the
axis X1 and that extend in a radial direction relative to the axis
X1. Meanwhile, a pair of restricted faces 15a (example of a
restricted portion) are formed in the vicinity of an end portion on
a side face of the shaft member 15. The restricted faces 15a come
in contact with the rotation restricting faces 20a, respectively,
according to a rotation of the rotation member 10 relative to the
shaft member 15 in an arrow A direction in FIG. 5. Further, as
shown in FIGS. 5 and 6, the rotation transmitting mechanism
includes a coil spring 18 for biasing the rotation member 10 to
rotate relative to the shaft member 15 in a direction in which the
rotation restricting faces 20a and the restricted faces 15a are
pressed against each other. Because of the operation of the coil
spring 18, even if the rotation member 10 and the shaft member 15
are provided in a tiltable manner, the rotation of the shaft member
15 is transmitted without any delay to the rotation member 10
regardless of a rotation phase of the shaft member 15.
According to the other feature of the rotation angle detection
device of the present embodiment, a centering mechanism is provided
for retaining a rotation axis X2 of the rotation member 10 to match
the fixed axis X1 of the housing 5 regardless of the tilting of the
shaft member 15 relative to the housing 5, which may be caused when
the sensor lever 16 is operated to rotate by means of the pedal
lever 3a. As shown in FIGS. 2 and 3, the centering mechanism
includes an inclined face 6a annularly formed along a base portion
of the boss portion 6 of the housing 5. The coil spring 18
constantly biases or presses an annular edge portion 12a formed at
axially one end of the magnet holder 12 to a substantially middle
portion of the inclined face 6a. The inclined face 6a extends in a
circumferential direction with reference to the fixed axis X1 in a
rotational symmetry state. In view of a cross-section passing
through the fixed axis X1 of the housing 5, the inclined face 6a is
inclined by approximately 45 degrees relative to the fixed axis
X1.
The edge portion 12a of the magnet holder 12 forms an exterior
angle of approximately 100 degrees relative to the fixed axis X1 of
the housing 5 in the cross-section passing through the fixed axis
X1. The edge portion 12a is smoothly slidable on the inclined face
6a of the housing 5. A diameter of the inner peripheral face of the
magnet holder 12 is sufficiently larger than the outer diameter of
the boss portion 6 of the housing 5 so that the magnet holder 12 is
relatively rotatable to the boss portion 6 in a state where the
inner peripheral face of the magnet holder 12 is not in contact
with the boss portion 6. Accordingly, as shown in FIG. 7A, when the
edge portion 12a of the rotation member 10 is biased and pressed to
the inclined face 6a by the coil spring 18, the edge portion 12a
tends to be positioned concentrically on the inclined face 6a with
reference to the fixed axis X1. This circumstance is equal to a
principle in which a ring, for example, placed on a generatrix of a
circular cone standing straight is most stable in a state where,
due to its own weight, a center axis of the circular cone and an
axis of the ring match each other. As a result, the rotation member
10 is automatically controlled to a state where the axis X2 thereof
matches the fixed axis X1 of the housing 5.
As mentioned above, the coil spring 18 biases the rotation member
10 to rotate in the arrow A direction (see FIG. 5) relative to the
shaft member 15, and also biases a portion of the rotation member
10 to be pressed against the inclined face 6a of the housing 5. As
shown in FIG. 2, at least a half length of the coil spring 18 is
received within a cylindrical-shaped protection wall 5d formed so
as to project in parallel to the bearing 5c from an inner face of
the cover member 5b. Then, as shown in FIGS. 2 and 5, one end 18a
of the coil spring 18 engages with a hook portion 11g formed by
bending a portion of a bottom portion of the yoke main body 11 in a
downward direction, i.e. rightward direction in FIG. 3, while the
other end 18b of the coil spring 18 engages with a portion on a
base side of the protection wall 5d of the cover member 5b of the
housing 5, instead of the shaft member 15. As a result, the coil
spring 18 biases the sensor lever 16 to its home position via the
rotation member 10 and the shaft member 15, and also functions as a
return spring for retaining the sensor lever 16 to engage with the
pedal lever 3a regardless of a rotating state of the pedal lever
3a.
The housing 5 can be made of PBT (polybutylene terephthalate), for
example, and the magnet holder 12 biased and pressed against the
inclined face 6a can be made of PA6 (Nylon 6), for example, that
includes molybdenum disulfide so that the magnet holder 12 can have
a sliding durability.
Depending on a coefficient of friction between the inclined face 6a
of the boss portion 6 of the housing 5 and the edge portion 12a of
the magnet holder 12, an annular-shaped inclined face 26a shown in
FIG. 7B that has an inclination less than 45 degrees relative to
the fixed axis X1 in the cross-section passing through the fixed
axis X1 may better achieve a sufficient centering function even if
the biasing force along the fixed axis X1 by the coil spring 18 is
specified smaller. If the biasing force by the coil spring 18 is
able to be defined smaller, the inclined face 6a or the edge
portion 12a of the magnet holder 12 may be prevented from abrading
away due to friction thereof. However, excessively small
inclination of the inclined face may cause difficulty in sliding of
the edge portion 12a of the magnet holder 12 on the inclined face
6a. Thus, the inclination of the inclined face can be specified in
a range between 15 degrees and 40 degrees.
As shown in FIG. 7C, an inclined face 36a having an arc shape of
which a center is positioned within the annular edge portion 12a of
the rotation member 10 can be provided instead of the inclined face
having a linear shape in view of the cross-section passing through
the fixed axis X of the housing 5. However, in this case, a tangent
passing on a contact point between the annular edge portion 12a and
the inclined face 36a may form an angle between 15 degrees and 40
degrees relative to the fixed axis X1 in a state in which the
rotation member 10 and the housing 5 are concentric.
Alternatively, according to the centering mechanism as shown in
FIG. 7D, an inclined face 46a may be formed at axially one end of
the rotation member 10 so as to extend annularly. In addition, a
projecting portion (edge portion) 50a may be formed on an outer
periphery of the base portion of the boss portion 6 of the housing
5 so as to annularly extend with reference to the fixed axis
X1.
Further alternatively, according to the centering mechanism as
shown in FIG. 7E, an inclined face 56a is formed on an inner
peripheral face of a cylindrical-shaped receiving portion 51t that
is formed to extend from an outer edge of the housing 5. Then, an
annular edge portion 41a formed in the vicinity of a tip end of an
outer peripheral face of the magnet holder 12 may be slidable to
the inclined face 56a.
Still further alternatively, according to the centering mechanism
as shown in FIG. 7F, the inclined face 6a is formed along the outer
periphery of the base portion of the boss portion 6 of the housing
5, and the inclined face 56a is formed on an inner peripheral face
of the cylindrical receiving portion 51t that is formed to extend
from an outer edge of the housing 5. Then, the annular edge portion
12a formed at axially one end of the magnet holder 12 and the
annular edge portion 41a formed in the vicinity of the tip end of
the outer peripheral face of the magnet holder 12 are slidable to
the inclined faces 6a and 56a, respectively.
The aforementioned inclined faces 6a, 26a, 36a, and 46a, and the
edge portions 12a, 41a, and 50a each may not have a continuous
annular shape forming a perfect circumference, and each may have
multiple inclined faces or multiple edge portions as interrupted at
several portions on each circumference, as long as the edge portion
of the magnet holder 12 is smoothly slidable on the inclined face
within an area where the rotation member 10 is rotated on the basis
of the rotation of the pedal arm 3. When at least one of the
inclined face and the edge portion of the magnet holder is divided
into multiple contact faces, friction between the inclined face and
the edge portion of the magnet holder, and abrasion due to that
friction may be decreased.
Further, the other form of a spring instead of the coil spring may
be used as a biasing means for biasing the rotation member 10 to
rotate in the arrow A direction relative to the shaft member 15,
and for biasing a portion of the rotation member 10 to be pressed
against the inclined face 6a of the housing 5 as a part of the
centering mechanism. For example, the biasing means can be
constituted by a spring having a ring-shaped base portion fixed to
the housing, and multiple plate-shaped or pin-shaped pieces
obliquely extending from multiple portions at the base portion to a
bottom portion of the rotation member 10.
Furthermore, a first biasing means for biasing the rotation member
10 to rotate in the arrow A direction relative to the shaft member
15, and, as a part of the centering mechanism, a second biasing
means for biasing a portion of the rotation member 10 to be pressed
against the housing 5 may be constituted by respective springs. In
this case, for example, the second biasing means can be constituted
by a plate spring, and the like, instead of a coil spring.
The present embodiment can be employed in a rotation angle
detection device for detecting a rotation angle of an operated
member that is operated to rotate by means of a control pedal of a
vehicle.
According to the aforementioned embodiment, even if the shaft
member 15 is tilted relative to the housing 5 because of the
rotation operation of the sensor lever 16, the rotation axis X2 of
the rotation member 10 is constantly retained in a predetermined
position relative to the fixed axis X1 of the housing 5 by means of
the centering mechanism. Thus, a certain level of rotation angle
detection accuracy can be obtained.
Further, according to the aforementioned embodiment, the rotation
member 10 is connected to the shaft member in a tiltable manner.
Thus, even if a looseness is present in a rotation direction
between the rotation member 10 and the shaft member 15, the
rotation restricting face 20a and the restricted face 15a are
retained so as to be contact with each other by means of a biasing
force of the coil spring 18 in the rotational direction.
Accordingly, a relative angle between the rotation member 10 and
the shaft member 15 is retained at a constant level thereby surely
detecting the rotation angle of the sensor lever 16. In addition, a
biasing means for biasing the rotation member 10 to be pressed
against the annular-shaped inclined face and a biasing means
provided for eliminating a looseness of the rotation member 10
relative to the shaft member 15 can be combined into a single
biasing means of a coil spring shape.
The principles, preferred embodiment and mode of operation of the
present invention have been described in the foregoing
specification. However, the invention which is intended to be
protected is not to be construed as limited to the particular
embodiments disclosed. Further, the embodiments described herein
are to be regarded as illustrative rather than restrictive.
Variations and changes may be made by others, and equivalents
employed, without departing from the spirit of the present
invention. Accordingly, it is expressly intended that all such
variations, changes and equivalents which fall within the spirit
and scope of the present invention as defined in the claims, be
embraced thereby.
* * * * *